The two are considered topologically equivalent as each has a hole—the ear of the mug and the centre of the donut. In the metaphor, the mug and the donut are one and the same. If they were made out of rubber, one could be twisted and stretched into the shape of the other without changing its essence. A strange universe of fundamental shapes long existing only in mathematics, the field was introduced into the physics realm just a few decades ago.

You can put your finger through the hole in a teacup handle, but you can't put it through a potato, so these are two different categories of topological objects," explained Manuel Asorey of the University of Zaragoza's department of theoretical physics. Donut muffins are of my favorite desserts to make. I often make them as mini muffins or as mini donuts. I’ve been wanting to make a mug cake version for a very long time, but never got around to it until now. After a few tries, I got exactly what I was looking for. This isn’t quite the same as some of the other mug cakes I’ve made in the past. I didn’t create a recipe that can be made into one single serving, but it’s still delicious and easy and you can always store the leftover batter for later. Of course, if you are just making this for yourself, you don’t need to bother with all the decorations. You can also do a simple cinnamon sugar topping, which is what I usually do for my donut muffins. At first, I was just going to add some chocolate ganache and sprinkles on top. And then, I decided to have some fun. Using a cupcake corer, I cut into the tops of my donut cakes so that they look like donuts. I didn’t actually remove the entire center as I wanted to keep as much cake in there as possible. So I stopped my corer about halfway down. The hole in the middle is deep enough to make it look like a donut, but you don’t actually lose too much precious cake.The donut taste is similar to cake donuts and comes from the mini donut muffin recipe that’s been widely shared on the internet. I bought this cupcake corer years ago, convinced I was going to make fancy stuffed cupcakes. Which never happened. Who knew it would come in handy for making donut mug cakes? I never met a doughnut I didn’t like. Ring or filled, posh or high street, they speak to me. A Krispy Kreme with a peanut butter centre is basically my religion. So, I’m drawn to this strange mug. The idea of stirring a brew, dreaming of doughnuts, isn’t horrible. And it’s arguably clever: think about the visual pun of the glaze, crucial to both pottery and doughnuts. The porcelain paint here is applied in the happy slapdash of fauvism, woozy pink icing and Technicolor sprinkles capturing the narcotic quality of childhood memory.

Even though this doesn’t make just one single serving, you can refrigerate the rest of the batter for later. Or you can make a few mug cakes rather than having to take the time to make mini donuts or mini donuts in the oven. If you’re impatient like me, being able to eat the donut cake in one minute rather than 10-15 is a definite plus. The quip describes it perfectly: topology explains how a material's shape can be completely deformed into new one without losing its core properties.This single serving mug cake tastes just like baked old fashioned donuts or the baked donut muffins that became popular a few years ago. But instead of having to make an entire batch, you can make an individual one in just minutes.